The present invention relates broadly to head mounted display devices, and in particular to an anti-flutter apparatus for these devices.
Systems have been proposed for remotely viewing a scene by means for a closed-circuit television system or the like. Some of these prior art systems have included means for remotely controlling the remote location. Attempts have been made in the past to coordinate the movement or control of the remote pickup with the movement of the remote observer's eyes or head in order to inject an element of realism into the remote presentation. These systems of the prior art have the disadvantage that the movement of the observer is unduly restricted, the field of view at the remote location is severely limited, the method of control is unduly complex and/or the nature of the display on the indicator is such that the observer lacks the subjective feeling of being present at the remote location or scene pickup. These and other disadvantages of prior art systems have made them inapplicable to such complex tasks as landing a high-speed aircraft either from a point within the plane or at some remote location on the ground controlling a highly maneuverable submarine, traffic surveillance, etc.
Head mounted infinity display visual systems which present a new scene at discrete intervals develop an oscillation (flutter) problem if the scene display is repeatedly updated to display a stationary image with respect to the earth. The problem arises when the visual system is trying to react to head position rotation by generating new scenes at discrete intervals. The displayed scene moves with the head until update time whereupon the scene appears to jump back to its correct position with respect to the earth. For example, if the scene display was being updated by a computer image generator 30 times per second, and the head was turning horizontally at a rate of 30 degrees per second, then the perceived flutter of the image would have an amplitude of up to 1 degree and a frequency of 30 Hz. Another problem which the present invention greatly reduces is the transport delay or lag between head movement and the display system response.